Heretofore in wide use as motor vehicle air conditioner evaporators are those of the so-called stacked plate type which comprise a plurality of flat hollow bodies arranged in parallel and each composed of a pair of dishlike plates facing toward each other and brazed to each other along peripheral edges thereof, and a louvered corrugated fin disposed between and brazed to each adjacent pair of flat hollow bodies. In recent years, however, it has been demanded to provide evaporators further reduced in size and weight and exhibiting higher performance.
To meet such a demand, the present applicant has already proposed an evaporator which comprise a heat exchange core composed of tube groups in the form of two rows arranged in parallel in the front-rear direction and each comprising a plurality of heat exchange tubes arranged at a spacing, a refrigerant inlet-outlet tank disposed at the upper end of the heat exchange core and a refrigerant turn tank disposed at the lower end of the heat exchange core, the refrigerant inlet-outlet tank having its interior divided by a partition into a refrigerant inlet header positioned on the front side and a refrigerant outlet header positioned on the rear side, the inlet header being provided with a refrigerant inlet at one end thereof, the outlet header being provided with a refrigerant outlet at one end thereof alongside the inlet, the refrigerant turn tank having its interior divided by a partition wall into a refrigerant inflow header positioned on the front side and a refrigerant outflow header positioned on the rear side, the partition wall of the refrigerant turn tank having a plurality of refrigerant passing holes formed therein and arranged longitudinally of the wall at a spacing, the heat exchange tubes of the front tube group having upper ends joined to the inlet header, the heat exchange tubes of the rear tube group having upper ends joined to the outlet header, the heat exchange tubes of the front tube group having lower ends joined to the inflow header, the heat exchange tubes of the rear tube group having lower ends joined to the outflow header. The refrigerant flowing into the inlet header of the inlet-outlet tank flows through the heat exchange tubes of the front tube group into the inflow header of the turn tank, then flows into the outflow header through the refrigerant passing holes in the partition wall and further flows into the outlet header of the inlet-outlet tank through the heat exchange tubes of the rear tube group (see the publication of JP-A NO. 2003-75024).
The evaporator disclosed in the above publication is reduced in weight and improved in performance, so that larger quantities of condensation water are produced over the surfaces of corrugated fins than in conventional evaporators of the stacked plate type, hence a larger amount of condensation water per unit volume of the evaporator. Consequently, the condensation water is likely to scatter about or freeze on the surfaces of corrugated fins to result in an impaired heat exchange efficiency. With evaporators, the condensation water produced on the surfaces of fins usually falls through the clearances between louvers. A higher drainage efficiency is therefore available by increasing the length of louvers. However, to ensure compactness and reduced weight as in the case of the evaporator of the above publication, there is a need to decrease the spacing between adjacent heat exchange tubes. Lengthening the louvers is accordingly limited.
An object of the present invention is to overcome the above problems and to provide an evaporator wherein the fin surfaces can be drained of condensation water efficiently.